Add a Reimu / Marisa-like selectable player character system in my game - Why not?

Akira here!

While I'm resting upstairs, I just think about how about bringing Yumemi's fanmade daughter back after hearing this dope-@$ track, in addition with Aya, who I already added into my fangame series.

Now I want to make Yumemi's daughter does not throw cards like crazy; instead Aya will throw a fecking ton of cards at enemies in order to exorcise them (literally!).

I renamed the daughter into Mari Okazaki (kanji here: 岡崎茉莉). The name of this character should not to be confused with the real-life runner Mari Ozaki. I named her like that in order to pay homage to MARI of the game OMORI, which my fangame series drew heavy inspirations from., but not a clone of.

Well, my head get clonked after thinking about what I need to fill in here, so let's say I'm going to add the two characters as selectable player characters in my fangame series, in a manner similar to Reimu and Marisa from the mainline Touhou games being playable in most games.